1. Field of the Invention
The present invention relates to a microwave oven capable of reducing high frequency electric waves leaking from a heating chamber of the oven that may interfere with the wireless LAN communication on board an aircraft.
2. Description of the Related Art
A microwave oven, which is one type of a high frequency heating apparatus, utilizes the heat generation effect of microwaves in the 2.45 GHz frequency range.
The oscillating frequency of the microwave oven and the frequency of the wireless LAN (local area network) communication utilize the same ISM (industrial scientific medical) band of 2.45 GHz, so the electromagnetic noises generated from the microwave oven may interfere with the wireless LAN communication and may cause communication errors.
On the other hand, the need for internet services on board the aircraft has increased during recent years, and the need for coexistence of microwaves ovens indispensable for the customer services provided on the aircraft and the wireless LAN communication has made it necessary to reduce the electromagnetic noises generated during operation of the microwave oven.
In general, most of the microwave ovens available in the market have choke structures formed to the door for attenuating electric waves as measures for preventing the leakage of output electric waves from the heating chamber to the exterior.
Further, a punching metal plate having many holes with a diameter approximately 1 mm for shielding electric waves is attached to the window for observing the inside of the heating chamber on the door of the microwave oven, for preventing leakage of electric waves through the door.
The prior art microwave oven equipped with a door having a choke structure for attenuating leaked electric waves and a punching metal plate for shielding the leaked electric waves is disclosed in Japanese Patent Application Laid-Open Publication No. 5-26458 (patent document 1) and Japanese Patent Application Laid-Open Publication No. 2000-97441 (patent document 2).
However, according to the microwave ovens disclosed in patent documents 1 and 2, the electric waves that could not be shielded by the choke structure and the punching metal plate on the door leak out to the exterior, which is a significant amount of electric wave leakage considering the electric field strength level of wireless LAN communication, and interferes with the wireless LAN communication.
Therefore, it is necessary to further suppress the leakage of electric waves in the 2.45 GHz band that could not be shielded by the choke structure and the punching metal plate mainly equipped to the conventional microwave ovens.
However, with respect to the method for suppressing leakage of electric waves in the 2.45 GHz band, the tampering with the choke structure of the door on the microwave oven conflicts with the DHHS (Department of Health and Human Services) standard, so it is necessary to reduce the electric waves leaking out to the exterior of the heating chamber of the microwave oven without adding any arrangement to the choke structure.